1. Technical Field
The present disclosure relates to a nonvolatile memory device and a method for manufacturing the same. More specifically, the present disclosure relates to a nonvolatile memory device that memories data using a material whose resistance value changes reversibly as a result of application of an electrical signal and a method for manufacturing the nonvolatile memory device.
2. Description of the Related Art
Recently, with the progress of digital technologies, higher functionality of electronic devices such as portable information devices and intelligent household electrical appliances has been increasingly realized. With the realization of high performance of these electronic devices, miniaturization and high-speed operation of semiconductor elements used in the electronic devices have rapidly proceeded. In particular, applications of nonvolatile memory having a large storage capacity, such as flash memory, have been rapidly increasing. Furthermore, with regard to a next-generation novel nonvolatile memory to replace flash memory, research and development of a resistance-variable nonvolatile semiconductor memory element using a so-called resistance-variable element has progressed. Herein, the term “resistance-variable element” refers to an element having a property in which the resistance value can be reversibly changed by an electrical signal. The resistance-variable element is capable of storing data corresponding to this resistance value in a nonvolatile manner.
International Publication No. 2012/063495 (Patent Literature 1) discloses a method for manufacturing a nonvolatile semiconductor memory element that includes a resistance-variable element formed on a contact plug, the nonvolatile semiconductor memory element including a lower electrode, a resistance-variable layer, and an upper electrode. The method includes, before a step of forming the lower electrode by pattering a first conductive film, a step of oxidizing an edge of the resistance-variable layer so as to provide an insulating property.
International Publication No. 2013/057920 (Patent Literature 2) discloses a nonvolatile memory element including a first wiring, a first plug that is disposed on the first wiring and electrically connected to the first wiring, a degeneration prevention layer that covers the entire region of an upper surface of the first plug and has electrical conductivity, a resistance-variable element that covers a part of an upper surface of the degeneration prevention layer and that is electrically connected to the first plug with the degeneration prevention layer therebetween, and a second wiring that is disposed on the resistance-variable element and electrically connected to the resistance-variable element. In the nonvolatile memory element, the resistance-variable element includes a resistance-variable layer whose resistance state changes reversibly on the basis of an electrical signal applied, and a horizontal cross section of a lower surface of the degeneration prevention layer is equal to a horizontal cross section of the upper surface of the first plug.